1. Field of the Invention
The present invention relates to a controller of an AC motor.
2. Discussion of the Background
In controllers of AC (alternating current) motors, their driving control in a constant output region is generally the control of setting a current command on the d axis, which is parallel to the flux of the AC motor, into the negative direction, thereby weakening the flux. This control is also referred to as voltage limiting control (see, for example, Japanese Unexamined Patent Application Publication No. 2010-022165).